Textbook of Veterinary Nuclear Medicine

2011 Radiation Oncology Exam Cases

Radiation Biology

1. If you analyze levels of gH2AX expression of tumor cells (i.e. by immunocytochemistry) after a 6 Gy radiation exposure at several timepoints after radiation, which of the following would you expect to see? (1 point)

A) The irradiated cells would show progressively increasing levels of gH2AX at 1, 6, and then 24 hours after irradiation
B) The irradiated cells would show progressively decreasing levels of gH2AX at 1, 6, and 24 hours after irradiation
C) The irradiated cells would show an increase in gH2AX at 1 hour after irradiation and then progressively decreased gH2AX at 6 and 24 hours after irradiation
D) The irradiated cells would show progressively increasing levels of gH2AX at 1 and 6 hours after irradiation and then decreased levels at 24 hours after irradiation

2. Which one (1) of the following is TRUE regarding the difference between an "effective survival curve" for multi-fraction irradiation and a single dose single hit multi-target survival curve? (1 point)

A) The D0 for an effective survival curve is equal to that of a single dose survival curve.
B) The slope of an effective survival curve is more shallow than that of a single dose
survival curve.
C) The D10 for an effective survival curve is less than that of a single dose survival
curve.
D) The single dose survival curve is to the right of an effective survival curve.

General, Basic and Clinical Knowledge

Several retrospective studies of apocrine gland carcinoma of the anal sac in dogs have been published. Indicate whether the following statements are TRUE or FALSE. (1 point each)

1. TRUE or FALSE: The presence of lymph node metastasis is a consistent negative prognostic indicator.

2. TRUE or FALSE: Overall median survival times in treated patients in the recent literature are greater than one year.

Physics

1. Kerma is the: (1.5 points)

A. Energy per unit mass absorbed along the path of a charged particle
B. Energy per unit mass transferred from photons to charged particles
C. Energy per unit mass transferred from charged particles
D. Charge released by photons as they pass through a specified amount of air

2. Which one of the following best describes the difference between x-rays and gamma-rays? (1.5 points)

A. Energy

B. Origin

C. Charge

D. Velocity

E. All of the above

Clinical

1. Evaluate the following (Cobalt-60) treatment plan. The anatomic part is a transverse section through a thigh. The femur is shown, and the PTV is the stippled area. Beam one (1) is at zero (0) on the machine gantry and the gantry rotates clockwise. Based on this information, please answer the following questions.

See image from Clinical Case #1 below

A) TRUE or FALSE: The plan is adequate for treatment of the tumor. (1 point)

A. True
B. False

B) Which one (1) of the following treatment plan adjustments would be most likely to result in lymphedema in the future? (2 points)

A. Addition of a beam at 90

B. Addition of a beam at 90 and 270

C. Electron therapy

D. Addition of a beam at 180

C) Which one (1) of the following treatment plan adjustments will most improve dose distribution across the tumor and spare normal tissue? (2 points)

A. Addition of a beam at 90

B. Addition of a beam at 90 and 270

C. Electron therapy

D. Addition of a beam at 180

2. Contrast enhanced CT images from a South African cabybara from the local zoo are available for review (CT series, images 46). She presented with blindness and inability to navigate her exhibit pool.

See image from Clinical Case #2 below (Note: only one image of the series is shown)

A) Which one (1) of the following would best describe the images and most likely differential diagnoses? (2 points)